Extended half-life factor IX prophylaxis up to every 21 days in hemophilia B: a longitudinal analysis of the efficacy and safety in selected adult patients

•Extended half-life factor IX products enable prolonged individualized dosing intervals.•Some patients with hemophilia B can extend rIX-FP dosing regimens from 7 days to 14 or 21 days.•rIX-FP is well tolerated with low annualized bleeding rates.•Long-term efficacy and safety of extended half-life rIX-FP are confirmed in adults.